TITLE:   GCN CIRCULAR
NUMBER:  43297
SUBJECT: GRB 260101A: Fermi GBM Observation
DATE:    26/01/02 05:59:57 GMT
FROM:    Glowbug DEV <boyan.a.hristov@nasa.gov>

B. Hristov (UAH) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:

"At 00:56:30.65 UT on 01 January 2026, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 260101A (trigger 788921795/260101039).
which was also detected by Swift (S. B. Cenko et al. 2026, GCN 43285), SVOM/GRM
(Z. Yu et al. 2026, GCN 43292) and GECAM-B (C. Wang et al. 2026, GCN 43294).
The Fermi GBM on-ground location is consistent with the one reported by Swift.

The angle from the Fermi LAT boresight is 43 degrees.

The GBM light curve consists of multiple emission episodes with a duration (T90)
of about 27.4 s (50-300 keV). The time-averaged spectrum
from T0 to T0+29.6 s s is best fit by
a power law function with an exponential
high-energy cutoff.  The power law index is -1.09 +/- 0.01 and
the cutoff energy, parameterized as Epeak, is 143.5 +/- 1.5 keV.

The event fluence (10-1000 keV) in this time interval is
(6.7 +/- 0.12)e-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+25 s in the 10-1000 keV band is 9.6 +/- 0.3 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
sftp://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html

For Fermi GBM data and info, please visit the official Fermi GBM Support Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"